Directions

In a large saucepan, over moderate heat, heat oil 1 minute. Add onion and sauté, stirring occasionally, until limp — about 5 minutes. Add zucchini, dill, and stock, and bring to a boil. Reduce the heat to low and simmer, uncovered, until zucchini is tender — 8 to 10 minutes; remove from the heat and cool slightly. Working in batches, purée the zucchini mixture in a blender at high speed or in a food processor. Mix in salt and pepper. Pour into a large bowl, cover, and refrigerate up to 3 hours.

Meanwhile, to prepare croutons: cut 1/2-inch thick slices of bread and trim off the crusts. Using a sharp utility knife, cut the slices of bread into 1/2-inch cubes. Melt butter over moderate heat in a large skillet. Stir in olive oil and heat until bubbly. Add bread cubes in a single layer. As croutons brown, turn with tongs. When browned on all sides, remove to a plate covered with paper towelling and drain. Use warm or at room temperature.

To serve, ladle thoroughly chilled soup into 6 soup plates and top with croutons.